Vessel

Abstract

To provide a vessel which is less likely to generate a loss of propulsion force.SOLUTION: A vessel 10 includes a hull 1 having a bottom 5 and a propulsion device 2. The propulsion device 2 has a propeller 23 capable of rotating with a propeller shaft 22 as a center piercing a shaft hole 51 in the bottom 5 and propulsion force is generated for sailing the hull 1 by rotation of the propellers 23. The hull 1 has a groove unit 52 having length in a front to back direction D2 in the periphery of the propeller 23 on the bottom 5. The shaft hole 51 is disposed in the groove unit 52.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a vessel that generates propulsive force for propelling the vessel by rotation of a propeller. [Background technology]

[0002] As a related art, a ship is known that includes a hull and a propeller (propeller structure) or the like as a propulsion device (propulsion structure) for obtaining propulsion force (see, for example, Patent Document 1). The ship according to the related art is a twin-screw ship that employs a twin-screw propulsion device in which two propeller shafts extending parallel to each other are used, and a propeller is attached to each propeller shaft.

[0003] In a vessel according to the related art, the propeller is rotatably supported on a bossing extending rearward from the bottom of the vessel and rotates in accordance with the rotation of the propeller shaft (propeller shaft member). The propeller generates a propeller water current toward the rear, thereby generating a thrust that propels the vessel forward. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-93503 Summary of the Invention [Problem to be solved by the invention]

[0005] In a configuration in which the propeller is located on the bottom of the ship, as in the related art described above, water turbulence can occur around the propeller shaft when the ship is sailing, and this water turbulence can result in a loss of propulsion force.

[0006] An object of the present disclosure is to provide a vessel that is less susceptible to loss of propulsive force. [Means for solving the problem]

[0007] A vessel according to one aspect of the present disclosure includes a hull having a bottom and a propulsion device. The propulsion device has a propeller rotatable about a propeller shaft passing through a shaft hole in the bottom, and rotation of the propeller generates a propulsive force for propelling the hull. The hull has a groove portion on the bottom of the hull that extends in the fore-and-aft direction around the propeller. The shaft hole is disposed within the groove portion. [Effects of the Invention]

[0008] According to the present invention, a ship in which loss of propulsive force is less likely to occur can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view of a ship according to a first embodiment as viewed from the deck side. [Figure 2] FIG. 2 is a schematic right side view of the vessel according to the first embodiment. [Figure 3] FIG. 3 is a schematic perspective view of the ship according to the first embodiment as viewed from the bottom side. [Figure 4] FIG. 4 is a schematic bottom view of the vessel according to the first embodiment. [Figure 5] FIG. 5 shows a main part of the vessel according to the first embodiment, and is an enlarged view of an area Z1 in FIG. [Figure 6] FIG. 6 shows a main part of the vessel according to the first embodiment, and is an enlarged view of an area Z1 in FIG. [Figure 7] FIG. 7 shows a main part of the watercraft according to the first embodiment, and is a schematic rear view of the lower part of the hull as seen from the rear. [Figure 8] FIG. 8 is a cross-sectional view taken along the line Y1-Y1 in FIG. [Figure 9] 9A to 9C are cross-sectional views taken along lines X1-X1, X2-X2, and X3-X3 in FIG. [Figure 10] FIG. 10 is a schematic perspective view showing the main parts of the ship according to the first embodiment and the ship according to the comparative example, as viewed from the bottom side of the ship. [Figure 11]FIG. 11 is a schematic bottom view showing the main parts of the ship according to the first embodiment and the ship according to the comparative example. [Figure 12] FIG. 12 is an explanatory diagram showing simulation results of water currents in the ship according to the first embodiment and the ship according to the comparative example. [Figure 13] FIG. 13 is an explanatory diagram showing simulation results of water pressure in the ship according to the first embodiment and the ship according to the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The following embodiments are examples of specific embodiments of the present disclosure and are not intended to limit the technical scope of the present disclosure.

[0011] (Embodiment 1) [1] Overall structure First, the overall configuration of a boat 10 according to this embodiment will be described with reference to FIGS.

[0012] The vessel 10 is a mobile body that navigates (sails) on water such as the sea, a lake, or a river. In this embodiment, as an example, the vessel 10 is a "pleasure boat," which is a small vessel primarily used for sports or recreation on the sea. In this embodiment, the vessel 10 is configured to operate in response to operation (including remote operation) by a person (pilot), and is particularly a manned type that can be boarded by a person who is the pilot.

[0013] The vessel 10 comprises a hull 1, a propulsion device 2 (see FIG. 2), a rudder device 3 (see FIG. 2), and a cabin 4. The vessel 10 further comprises various onboard facilities, including an operating device that accepts operations by a person (pilot), a display device, various sensors (including detectors), various instruments, communication devices, control devices, and lighting equipment. Here, in FIGS. 1 and 2, the cabin 4 is schematically shown by an imaginary line (a two-dot chain line), and is not shown in the drawings other than FIGS. 1 and 2.

[0014] In this embodiment, as an example, the propulsion type of the boat 10 is an "inboard motor" in which the power source 21 (see FIG. 3) of the propulsion device 2 is mounted near the center of the hull 1, and the stern type (stern configuration) of the boat 10 is a "bracket type" (outboard propeller / outboard rudder type). As an example, the size of the hull 1 is assumed to be an overall length of 5 m to 20 m and a passenger capacity of approximately 5 to 15 people. Furthermore, in this embodiment, a semi-planing boat 10 is assumed with a speed-to-length ratio of 2.0 to 5.0. Therefore, although the boat 10 does not plank on the water surface with the hull (main hull 11) on the water, the boat 10 sails with the bow side of the hull 1 in a raised position.

[0015] In this embodiment, for ease of explanation, the vertical direction when the vessel 10 is stationary on the water is defined as the up-down direction D1. Furthermore, the fore-and-aft direction D2 and the left-and-right direction D3 are defined based on the direction as seen from the perspective of a person (pilot) sitting in the pilot's seat (inside the cabin 4) of the vessel 10. That is, the direction in which the vessel 1 moves when moving forward, i.e., the bow side (fore) as seen from the center of the vessel 1, is forward in the fore-and-aft direction D2, and the direction in which the vessel 1 moves when moving backward, i.e., the stern side (aft) as seen from the center of the vessel 1, is rear in the fore-and-aft direction D2. The port side as seen from the center of the vessel 1 is left in the left-and-right direction D3, and the starboard side as seen from the center of the vessel 1 is right in the left-and-right direction D3. However, these directions are not intended to limit the direction in which the vessel 10 is used (the direction during use).

[0016] Furthermore, in this disclosure, "parallel" refers to a case where two straight lines on a plane do not intersect no matter how far they are extended, that is, a case where the angle between the two is exactly 0 degrees (or 180 degrees), as well as a case where the angle between the two is within an error range of a few degrees (for example, less than 10 degrees) from 0 degrees. Similarly, in this disclosure, "orthogonal" refers to a case where the angle between the two is exactly 90 degrees, as well as a case where the angle between the two is within an error range of a few degrees (for example, less than 10 degrees) from 90 degrees.

[0017] As an example, the hull 1 and cabin 4 are constructed primarily from FRP (Fiber Reinforced Plastics). This allows the hull 1 and cabin 4 to be strong and lightweight while also offering a high degree of freedom in terms of shape, making it possible to realize a hull 1 with a variety of shapes. While Figures 1 and 2 show an example of a ship 10 with a flying bridge that has a maneuvering space above the cabin 4, a flying bridge is not essential.

[0018] The hull 1 has a hull main body 11 and a deck 12. The hull main body 11 constitutes the boat body (hull). The hull main body 11 has a length in the fore-and-aft direction D2, with the dimension in the left-right direction D3 being larger than the dimension in the up-and-down direction D1 (excluding the cabin 4) and the dimension in the fore-and-aft direction D2 being larger than the dimension in the left-and-aft direction D3. The hull main body 11 is formed in the shape of a box with an open top, and the power source 21 of the propulsion device 2 and the like are arranged inside.

[0019] The hull main body 11 has a pair of side shell plates 111, a rear side shell plate 112, and a bottom shell plate 113. The pair of side shell plates 111 are arranged opposite each other in the transverse direction D3 and form both side surfaces (ship sides) of the hull main body 11 in the transverse direction D3. The rear side shell plate 112 forms the rear surface (transom) of the hull main body 11. The bottom shell plate 113 forms the bottom 5, which is the underside of the hull main body 11. The pair of side shell plates 111, aft side shell plate 112, and bottom shell plate 113 are formed integrally (seamlessly) and form the outer hull of the hull main body 11.

[0020] The deck 12 is connected to the hull main body 11 so as to cover the opening surface (top surface) of the hull main body 11. In other words, the deck 12 constitutes the top surface of the hull main body 11 and is a deck on which people are expected to stand. If the hull main body 11 is divided into three parts in the fore-and-aft direction D2 and defined as bow, midship, and stern in order from the front (bow) side, the part of the deck 12 located at the bow (bow side) is the "bow deck," and the part located at the stern (stern side) is the "stern deck."

[0021] A cabin 4 is located in the center (midships) of the deck 12 in the fore-and-aft direction D2. Side aisles are provided on both sides of the cabin 4 on the deck 12 in the left-right direction D3, and people can move between the bow deck and the stern deck through the side aisles.

[0022] Furthermore, in this embodiment, the deck 12 is not at the same height throughout, but gradually becomes higher from the stern side to the bow side, and although not shown, has steps at the side passage and bow deck. Furthermore, a fall prevention fence (bow rail) may be provided around the deck 12 along the outer periphery from the bow deck located at the bow to the step at the side passage.

[0023] The hull 1 has a watertight space surrounded by a pair of side shell plates 111, aft side shell plate 112, and bottom shell plate 113 that form the outer hull of the hull main body 11, as well as the deck 12 (and the cabin 4). An engine room and the like are provided in the center of the watertight space in the fore-and-aft direction D2. Furthermore, a cabin and the like are provided forward of the engine room in the watertight space.

[0024] As shown in FIG. 2, the propulsion device 2 has a power source 21, a propeller shaft 22, a propeller 23, and a bracket 24.

[0025] The power source 21 includes, for example, an engine (internal combustion engine) that generates power by burning fuel. An example of the engine is a diesel engine that uses light oil as fuel. In this embodiment, as an example, the power source 21 further includes a power transmission unit that transmits the power generated by the engine to the propeller shaft 22. The power transmission unit includes, for example, a clutch and a reduction gear (marine gear), and has a function of switching between a transmission state in which power is transmitted from the engine to the propeller shaft 22 and a cut-off state in which power is not transmitted.

[0026] The propeller shaft 22 transmits power generated by the power source 21 to the propeller 23. The propeller shaft 22 is a cylindrical (round bar-shaped) shaft (propeller shaft) having a length along the fore-and-aft direction D2, and is arranged to pass through a shaft hole 51 (see FIG. 3) formed in the bottom shell plating 113 (ship bottom 5). The front end of the propeller shaft 22 is connected to the power source 21 inside the hull 1 (hull main body 11), and the rear end is connected to the propeller 23 outside the hull 1 (hull main body 11). In other words, the propeller shaft 22 mechanically connects the power source 21, which is arranged in a watertight space inside the hull 1, to the propeller 23, which is arranged outside the hull 1.

[0027] The propeller 23 is mechanically connected to the power source 21 via the propeller shaft 22 and is configured to be rotatable around the propeller shaft 22. The propeller 23 receives power generated by the power source 21 and rotates around the propeller shaft 22, thereby generating a propulsive force for moving the hull 1 forward or backward.

[0028] The bracket 24 is fixed to the bottom 5 of the vessel so as to protrude downward from the bottom 5, and rotatably supports the propeller shaft 22. Here, the bracket 24 supports the propeller shaft 22 in an inclined position relative to the bottom 5 of the vessel so that the rear end of the propeller shaft 22 connected to the propeller 23 is lower (slopes rearward) than the front end connected to the power source 21.

[0029] The propulsion device 2 is controlled in response to the operation of an operating device. For example, if the operating device includes an operating lever that can be rotated (moved) from a neutral position to a forward position and a reverse position, when the operating lever is in the neutral position, the propulsion device 2 does not generate propulsive force, and the propulsive force of the hull 1 is 0 (zero). In this case, to move the hull 1 forward, the operator operates the operating lever to rotate (move) it from the neutral position toward the forward position, and to move the hull 1 reverse, the operator operates the operating lever to rotate (move) it from the neutral position toward the reverse position. The propulsion device 2 increases the propulsive force (propeller rotation speed) for moving the hull 1 forward as the operation amount (rotation angle) of the operating lever from the neutral position toward the forward position increases.

[0030] As shown in Figure 3, the rudder device 3 is attached to the stern of the hull 1 and adjusts the direction of travel of the hull 1. In this embodiment, the rudder device 3 is located immediately behind the propeller 23 of the propulsion device 2. The rudder device 3 is controlled in response to the operation of an operating device. For example, if the operating device includes a steering wheel, the operator turns the steering wheel to cause the rudder device 3 to steer to starboard or starboard.

[0031] The cabin 4 has, for example, a cockpit at the top, and operating devices, display devices, various instruments, communication devices, etc. are arranged around the cockpit. The cabin 4 is arranged above the engine room, etc. The cabin 4 is configured to be accessible from the deck 12. The interior space of the cabin 4 is continuous with the space below the deck 12 (bow berth). Inside the cabin 4, for example, passenger seats, a table, a sink, a toilet, a shower room, a refrigerator, a utility box, a locker, etc. are arranged. Furthermore, the cabin 4 also has an engine room hatch, etc. for accessing the engine room.

[0032] 3 and 4, the vessel 10 according to this embodiment is a "two-engine, two-shaft" twin-screw vessel equipped with two propulsion devices 2. In other words, the vessel 10 employs a twin-shaft propulsion device 2 in which two propeller shafts 22 extending parallel to one another are used, and a propeller 23 is attached to each of the propeller shafts 22. Specifically, the vessel 10 is equipped with a pair of propeller shafts 22 aligned in the width direction of the hull 1 (left-right direction D3), and a pair of propellers 23 aligned in the width direction of the hull 1.

[0033] Furthermore, the vessel 10 also has a pair of power sources 21 and brackets 24, aligned in the width direction of the hull 1. The pair (two) propulsion devices 2 aligned in the width direction (left-right direction D3) of the hull 1 basically have a common configuration. The pair of propulsion devices 2 can be controlled individually, and it is possible, for example, to drive only the right-side propulsion device 2.

[0034] Similarly, the vessel 10 according to this embodiment also has two rudder gears 3. A pair (two) of rudder gears 3 aligned in the width direction (left-right direction D3) of the hull 1 are disposed immediately behind the pair of propellers 23.

[0035] The configuration of the hull main body 11 will be described in more detail below.

[0036] In the hull main body 11, the front ends (ends on the bow side) of a pair of side shell plates 111 are joined to each other to form the bow. The rear ends (ends on the stern side) of the pair of side shell plates 111 are joined to each other via the rear side shell plate 112, and together with the rear side shell plate 112, form the stern. In other words, the rear end of the port side side shell plate 111 is joined to the left end of the rear side shell plate 112, and the rear end of the starboard side side shell plate 111 is joined to the right end of the rear side shell plate 112.

[0037] Furthermore, the lower ends of the pair of side shell plates 111 and the lower end of the aft side shell plate 112 are joined to the bottom shell plate 113. In other words, the lower end of the port side side shell plate 111 is joined to the left end of the bottom shell plate 113 in the left-right direction D3, and the lower end of the starboard side side shell plate 111 is joined to the right end of the bottom shell plate 113. And the lower end of the aft side shell plate 112 is joined to the aft end of the bottom shell plate 113.

[0038] The pair of side shell plates 111 are shaped so that they move apart in the transverse direction D3 from the bow to the stern. In other words, the hull main body 11 has a shape in which the dimension in the transverse direction D3 (ship's width) gradually increases from the bow to the stern. The distance between the pair of side shell plates 111 is greatest midway in the fore-aft direction D2 of the hull main body 11, and the dimension in the transverse direction D3 of the hull main body 11 at this location matches the ship's width. The pair of side shell plates 111 are parallel to each other rearward of the location where the distance is greatest, all the way to the stern (rear side shell plate 112). The hull main body 11 may also have a shape in which the dimension in the transverse direction D3 (ship's width) gradually narrows from a midway point in the fore-aft direction D2 of the hull main body 11 toward the stern.

[0039] The pair of side shell platings 111 and the aft side shell plating 112 both protrude upward from the deck 12. That is, the upper ends of the pair of side shell platings 111 and the aft side shell plating 112 protrude upward from the deck 12 in a side view, and function as bulwarks (breakwaters) that prevent water (waves) from entering the deck 12. Water (seawater) that has entered the deck 12 is discharged outside the ship through outlets formed in the bulwarks. Beam materials are attached to the outer periphery of the bulwarks as buffer materials.

[0040] The hull main body 11 also has chines 116 formed at the joints between each of the pair of side shell plates 111 and the bottom shell plate 113. The chines 116 extend from the bow to the stern and are inclined relative to the horizontal plane so that they are positioned lower as they move toward the stern. The chines 116 are steps extending along the fore-and-aft direction D2 and are configured to protrude outward in the transverse direction D3 as they move upward from the steps. Therefore, when viewed from the same position in the fore-and-aft direction D2, the distance between the pair of side shell plates 111 in the transverse direction D3 is one step larger than the distance between the upper ends of the bottom shell plates 113.

[0041] The hull main body 11 has a fin-shaped skeg 117 (fin keel) that protrudes from the center of the bottom shell plating 113 in the left-right direction D3 and extends from the bow to the stern. The skeg 117 is provided from the front end (end on the bow side) of the bottom shell plating 113 to a midpoint in the fore-and-aft direction D2.

[0042] Furthermore, the hull main body 11 has a plurality of spray strips 119. In this embodiment, two spray strips 119 are provided on each of the port and starboard sides of the bottom shell plating 113 (a total of four spray strips 119). Each spray strip 119 extends from the bow to the stern and is inclined with respect to the horizontal plane so as to be positioned lower as it approaches the stern.

[0043] When the boat 10 is configured as described above, lift is generated by pressure changes caused by the water current flowing under the bottom of the boat. The bow of the boat 10 is raised at a sailing trim angle that corresponds to the lift. The generated lift becomes approximately equal to the hull weight when the boat speed exceeds a predetermined value. Therefore, when the boat 10 reaches a predetermined sailing speed or higher, the bow side of the boat 10 rises above the water, and the boat 10 sails in an attitude that allows the bottom (underside) of the stern side to glide on the water surface.

[0044] Furthermore, the hull 1 can employ various configurations in addition to those described above. For example, an anchor store for accommodating an anchor reel, an anchor store hatch, and the like are appropriately arranged on the bow deck, which corresponds to the bow portion of the deck 12. Furthermore, fishponds, lockers, inspection hatches (for the rudder 3, propeller, etc.), and the like are appropriately arranged on the stern deck, which corresponds to the stern portion of the deck 12. Furthermore, the hull main body 11 may have, for example, a knuckle line (spray strip), hull windows, and the like, as appropriate.

[0045] [2] Propulsion system peripheral structure Next, the structure surrounding the propulsion device 2 of the vessel 10 according to this embodiment will be described in more detail with reference to Figures 5 to 9. Since the propulsion device 2 is disposed at the rear of the vessel bottom 5, the detailed structure of the rear of the vessel bottom 5 will be described below.

[0046] Fig. 5 is an enlarged view of area Z1 in Fig. 3, and Fig. 6 is an enlarged view of area Z1 in Fig. 4. Fig. 7 is a schematic rear view of the lower part of the hull 1 as seen from the rear. Fig. 8 shows a cross-sectional view taken along line Y1-Y1 in Fig. 6, and Fig. 9 shows cross-sectional views taken along lines X1-X1, X2-X2, and X3-X3 in Fig. 6. The cabin 4 is also omitted from Figs. 5 to 9.

[0047] As described above, the ship 10 according to this embodiment is a twin-screw ship equipped with a pair (two) of propulsion units 2 that basically have a common configuration. The peripheral structure of the propulsion units 2 on the ship bottom 5 is configured symmetrically (left and right) with respect to the center line in the width direction (left-right direction D3) of the ship bottom 5. Therefore, unless otherwise specified, the left propulsion unit 2 and its peripheral structure will be described below, and a description of the right propulsion unit 2 and its peripheral structure will be omitted.

[0048] 5, 6, and 7, the hull 1 has a groove 52 around the propeller 23 on the bottom 5 of the ship, which is a recessed portion of the bottom 5 facing upward. The groove 52 has a length in the fore-and-aft direction D2. By providing the groove 52, it is possible to position the propeller shaft 22 as high as possible while avoiding interference between the propeller 23 and the bottom 5 of the ship.

[0049] The groove 52 is formed from the middle of the bottom 5 in the fore-and-aft direction D2 to the stern. That is, the groove 52 is open toward the rear. Here, as an example, the groove 52 has a rectangular shape with a length in the fore-and-aft direction D2 when viewed from below (see FIG. 6).

[0050] In this embodiment, the width dimension (dimension in the left-right direction D3) of the groove 52 is set larger than that of the propeller 23 so that the propeller 23 fits within the groove 52 in a bottom view (see FIG. 6). Furthermore, the propeller 23 is disposed closer to the bottom 5 so that at least a portion (upper portion) of the propeller 23 fits within the groove 52 in a rear view (see FIG. 7). Furthermore, the bracket 24 that supports the propeller shaft 22 is also fixed within the groove 52.

[0051] More specifically, in rear view, groove 52 has a generally arcuate shape that curves along an imaginary circle C1 (see FIG. 7) that is traced by the rotation of the blade tips of propeller 23. That is, a cross section of the bottom surface of groove 52 that is perpendicular to the longitudinal direction (front-rear direction D2) has a shape that follows an arc that is convex upward (a generally arcuate shape). In this way, groove 52 has a tunnel shape.

[0052] In the vessel 10 according to this embodiment, the shaft hole 51 formed in the vessel bottom 5 is disposed in the groove portion 52, as shown in Figures 5 and 6. That is, the shaft hole 51 formed in the vessel bottom 5 and through which the propeller shaft 22 passes is located inside the groove portion 52 so as to be accommodated within the groove portion 52.

[0053] In short, the vessel 10 according to this embodiment comprises a hull 1 having a vessel bottom 5, and a propulsion device 2. The propulsion device 2 has a propeller 23 that is rotatable about a propeller shaft 22 that passes through a shaft hole 51 in the vessel bottom 5. The propulsion device 2 generates a propulsive force for propelling the vessel 1 by rotation of the propeller 23. The vessel 1 has a groove 52 around the propeller 23 on the vessel bottom 5, the groove 52 having a length in the fore-and-aft direction D2. The shaft hole 51 is disposed within the groove 52.

[0054] According to this configuration, the shaft hole 51 formed in the bottom 5 is disposed in a groove 52 formed so as to be partially recessed relative to the bottom 5, thereby suppressing turbulence in the water flow around the shaft hole 51 and the propeller shaft 22 that protrudes below the bottom 5 through the shaft hole 51. Consequently, turbulence in the water flowing along the bottom 5 (particularly around the propeller 23) is suppressed, making it less likely that loss of propulsive force will occur due to turbulence in the water flow, and making it possible to provide a ship 10 that can generate propulsive force more efficiently.

[0055] Here, in this embodiment, the groove portion 52 is formed from the middle of the ship's bottom 5 in the fore-and-aft direction D2 to the stern. The shaft hole 51 is located rearward of the front end of the groove portion 52. In other words, as described above, the groove portion 52 is located at the rear of the ship's bottom 5 and is open rearward. Since the shaft hole 51 is located within such a groove portion 52, the shaft hole 51 is located rearward of the front end of the groove portion 52 in the fore-and-aft direction D2. In other words, the shaft hole 51 is located so as to fall within the range between the front and rear ends of the groove portion 52.

[0056] According to this configuration, the axial hole 51 formed in the bottom 5 of the vessel is located rearward of the front end of the groove portion 52, so that the turbulence of the water flow due to the influence of the axial hole 51 is less likely to occur, particularly when the vessel 1 is moving forward, and loss of propulsive force due to the turbulence of the water flow is less likely to occur.

[0057] 6, the amount of change in the width dimension of groove portion 52 in the front-rear direction D2 is 10% or less of the maximum value of the width dimension. That is, in a plan view, two sides of the outer periphery of groove portion 52 along the longitudinal direction (front-rear direction D2) are parallel. Therefore, the dimension of groove portion 52 in the width direction (left-right direction D3) is approximately constant over the entire length of groove portion 52 in the front-rear direction D2. More preferably, the amount of change in the width dimension of groove portion 52 in the front-rear direction D2 is 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% or less of the maximum value of the width dimension, and the sides may be completely parallel.

[0058] As a result, the dimension of the groove 52 in the width direction (left-right direction D3) becomes approximately constant, which reduces the likelihood of turbulence occurring in the water flowing within the groove 52 along the longitudinal direction (front-rear direction D2) of the groove 52. As a result, loss of propulsive force due to turbulence in the water flow is less likely to occur.

[0059] As described above, the ship 10 according to this embodiment is a twin-screw vessel equipped with a pair of propellers 23 aligned in the width direction (lateral direction D3) of the hull 1. As shown in FIG. 7 , the hull 1 has a pair of grooves 52 corresponding to the pair of propellers 23. In other words, a pair of grooves 52 each having a length in the longitudinal direction D2 is formed in the rear part of the bottom 5 of the hull 1. The pair of grooves 52 are symmetrical in the longitudinal direction D3, and a shaft hole 51 through which the propeller shaft 22 of each propeller 23 passes is disposed within each groove 52.

[0060] This suppresses turbulence in the water flow around the shaft hole 51 and the propeller shaft 22 that protrudes below the ship bottom 5 through the shaft hole 51, even in a twin-screw ship. Ultimately, this suppresses turbulence in the water flowing along the ship bottom 5 (particularly around the propeller 23), making it less likely that loss of propulsive force will occur due to turbulence in the water flow, and makes it possible to provide a ship 10 that can generate propulsive force more efficiently.

[0061] Furthermore, in a plan view, each of the pair of shaft holes 51 is located outward in the width direction (left-right direction D3) of the hull 1 with respect to a center P1 (see FIG. 6) in the width direction (left-right direction D3) of each of the pair of groove portions 52. In other words, the shaft holes 51 (and the propeller shaft 22 passing through the shaft holes 51) are not located at the center P1 in the width direction of the groove portions 52, but are disposed at a position offset outward from the center P1. Specifically, in the left propulsion unit 2, the shaft holes 51 and the propeller shaft 22 are located to the left of the center P1 in the width direction of the groove portions 52, and in the right propulsion unit 2, the shaft holes 51 and the propeller shaft 22 are located to the right of the center P1 in the width direction of the groove portions 52.

[0062] This allows the pair of propeller shafts 22 and the pair of propellers 23 to be arranged in a balanced manner in the width direction (left-right direction D3) of the hull 1, allowing the hull 1 to sail more stably when propulsion force is generated by the propulsion device 2.

[0063] 8, the bottom surface of the groove 52 has a curved shape that is convex upward in side view. In other words, the cross-sectional shape of the bottom surface of the groove 52 along the front-to-rear direction D2 is not linear, but has a curved shape that is convex upward. This makes it possible to suppress turbulence of the water flow caused by the propeller 23 and the ship bottom 5.

[0064] Furthermore, axial hole 51 is disposed in a recessed portion 53 that is recessed from the surrounding area in the bottom surface of groove portion 52. That is, a partially recessed recessed portion 53 is formed in the bottom surface of groove portion 52, and axial hole 51 is disposed in recessed portion 53. Specifically, as shown in FIG. 8 , axial hole 51 is disposed in a side wall facing rearward of the inner circumferential surface of recessed portion 53.

[0065] According to this configuration, since the shaft hole 51 formed in the bottom 5 of the ship is located in the further recessed portion 53 within the groove portion 52, particularly when the hull 1 is moving forward, it becomes difficult for the water flow to be disturbed by the influence of the shaft hole 51, and it becomes difficult for a loss of propulsion force due to the disturbance of the water flow to occur.

[0066] Also, as shown in FIG. 8, the groove portion 52 has a gradually increasing portion 520 that becomes deeper toward the stern side in at least a part of the front-rear direction D2 of the groove portion 52. In the present embodiment, the gradually increasing portion 520 is provided at least from the front end of the groove portion 52 to the fixing portion of the bracket 24. That is, at least from the front end of the groove portion 52 to the fixing portion of the bracket 24, the groove portion 52 is formed so as to gradually become deeper toward the stern side.

[0067] According to this configuration, at least in the gradually increasing portion 520, since the groove portion 52 gradually becomes deeper toward the stern side, compared with the case where the groove portion 52 suddenly becomes deeper, particularly when the hull 1 is moving forward, it becomes difficult for the water flow to be disturbed by the influence of the groove portion 52, and it becomes difficult for a loss of propulsion force due to the disturbance of the water flow to occur.

[0068] Here, the cross-section orthogonal to the front-rear direction D2 of the bottom surface of the groove portion 52 has a shape along an upwardly convex arc. The radius of curvature of the arc becomes larger toward the bow side at least in the gradually increasing portion 520. That is, as shown in FIG. 9, at least in the gradually increasing portion 520, the radii of curvature R1, R2, R3 of the cross-section orthogonal to the front-rear direction D2 of the bottom surface of the groove portion 52 become larger toward the bow side (R1 < R2 < R3). In other words, at least in the gradually increasing portion 520, the curvature of the cross-section orthogonal to the front-rear direction D2 of the bottom surface of the groove portion 52 becomes larger (tighter) toward the stern side. In the present embodiment in particular, at the front end of the groove portion 52, the radius of curvature R3 is very large, and the cross-section orthogonal to the front-rear direction D2 of the bottom surface of the groove portion 52 becomes substantially linear. That is, at the front end portion of the groove portion 52, the inside and the outside (front side) of the groove portion 52 in the front-rear direction D2 are seamlessly continuous.

[0069] This configuration can reduce the generation of negative pressure caused by a sudden change in flow velocity in the groove portion 52, at least in the gradually increasing portion 520. Therefore, loss of propulsive force caused by turbulence in the water flow is less likely to occur.

[0070] [3] Comparison with comparative examples Next, the operation of the peripheral structure of the propulsion device 2 of the boat 10 according to this embodiment in comparison with a comparative example will be described with reference to FIGS.

[0071] 10 and 11, the boat 10A according to the comparative example differs from the boat 10 according to this embodiment (referred to as "Example") in that the shaft hole 51 is located outside the groove portion 52. In the boat 10A according to the comparative example, the overall length (dimension in the fore-and-aft direction D2) of the groove portion 52 is shorter than that of the boat 10 according to this embodiment, and the shaft hole 51 is located forward of the front end of the groove portion 52.

[0072] Fig. 12 shows the results of a simulation of the water current flowing over the ship bottom 5 when the ship 10 according to this embodiment and the ship 10A according to the comparative example are traveling forward. As is clear from Fig. 12, the water current in front of (forward of) the propeller 23 is more linear in the ship 10 according to this embodiment. Therefore, the ship 10 according to this embodiment is less likely to experience loss of propulsive force due to turbulence in the water current than the ship 10A according to the comparative example.

[0073] 13 shows the results of a simulation of the water pressure around the ship bottom 5 when the ship 10 according to the present embodiment and the ship 10A according to the comparative example are traveling forward. As is clear from FIG. 13, the area in which negative pressure occurs around the propeller shaft 22 is narrower in the ship 10 according to the present embodiment. Therefore, the ship 10 according to the present embodiment is less susceptible to loss of propulsive force due to the influence of negative pressure than the ship 10A according to the comparative example.

[0074] [4] Variation Below, we will list some modified examples of embodiment 1. The modified examples explained below can be applied in appropriate combinations.

[0075] The vessel 10 is not limited to a pleasure boat, but may also be a merchant vessel including a cargo ship and a cargo-passenger ship, a work vessel including a tugboat and a salvage ship, a special vessel including a weather observation vessel and a training ship, a fishing boat, a naval vessel, etc. Furthermore, the vessel 10 is not limited to a manned type with a pilot on board, but may also be an unmanned vessel that can be remotely operated by a person (pilot) or that can operate autonomously.

[0076] Furthermore, the power source 21 is not limited to a diesel engine, and may include, for example, a gasoline engine or a motor (electric motor). Furthermore, the boat 10 may be equipped with a hybrid propulsion device 2 having multiple types of power sources 21, such as an engine and a motor. In this case, the power source 21 combines the power generated by the multiple types of power sources 21 and transmits it to the propeller 23.

[0077] [Appendix to the invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0078] <Appendix 1> a hull having a bottom; a propulsion device having a propeller rotatable around a propeller shaft passing through a shaft hole in the bottom of the vessel, and generating a propulsive force for propelling the vessel by rotation of the propeller, the hull has a groove portion having a length in the front-to-rear direction around the propeller on the bottom of the hull, The axial hole is disposed within the groove. ship.

[0079] <Appendix 2> The groove portion is formed from a midpoint in the fore-and-aft direction of the bottom of the vessel to the stern, The shaft hole is located rearward of the front end of the groove. Vessels as described in Appendix 1.

[0080] <Appendix 3> The change in width dimension of the groove in the front-rear direction is 10% or less of the maximum value of the width dimension. A vessel as described in Appendix 1 or 2.

[0081] <Appendix 4> The bottom surface of the groove portion has a curved shape that is convex upward in a side view. A vessel as set forth in any of Appendices 1 to 3.

[0082] <Appendix 5> The axial hole is disposed in a recessed portion recessed from the periphery at the bottom surface of the groove portion. A vessel as set forth in any of appendices 1 to 4.

[0083] <Appendix 6> The groove portion has a gradually increasing portion that becomes deeper toward the stern side in at least a part of the front-rear direction of the groove portion. A vessel as set forth in any of appendices 1 to 5.

[0084] <Appendix 7> a cross section of the bottom surface of the groove that is perpendicular to the front-rear direction has a shape that follows an upwardly convex arc, The radius of curvature of the arc increases toward the bow at least in the gradually increasing portion. Vessels as described in Appendix 6.

[0085] <Appendix 8> a pair of the propellers arranged in the width direction of the hull, The hull has a pair of the grooves corresponding to the pair of propellers. A vessel as set forth in any of Appendices 1 to 7.

[0086] <Appendix 9> Each of the pair of shaft holes is located on the outer side in the width direction of the hull with respect to the center in the width direction of each of the pair of groove portions in a plan view. Vessels as described in Appendix 8. [Explanation of symbols]

[0087] 1. Hull 2 Propulsion device 5. Ship's Bottom 10,10A ship 22 Propeller shaft 23 Propeller 51 Shaft hole 52 Groove 53 Recess 520 Gradual increase D2 Anteroposterior direction P1 center R1,R2,R3 Radius of curvature

Claims

1. a hull having a bottom; a propulsion device having a propeller rotatable around a propeller shaft passing through a shaft hole in the bottom of the vessel, and generating a propulsive force for propelling the vessel by rotation of the propeller, the hull has a groove portion having a length in the front-to-rear direction around the propeller on the bottom of the hull, The axial hole is disposed within the groove. ship.

2. The groove portion is formed from a midpoint in the fore-and-aft direction of the bottom of the vessel to the stern, The shaft hole is located rearward of the front end of the groove.

2. The watercraft of claim 1.

3. The change in width dimension of the groove in the front-rear direction is 10% or less of the maximum value of the width dimension.

3. A vessel according to claim 1 or 2.

4. The bottom surface of the groove portion has a curved shape that is convex upward in a side view.

3. A vessel according to claim 1 or 2.

5. The axial hole is disposed in a recessed portion recessed from the periphery at the bottom surface of the groove portion.

3. A vessel according to claim 1 or 2.

6. The groove portion has a gradually increasing portion that becomes deeper toward the stern side in at least a part of the front-rear direction of the groove portion.

3. A vessel according to claim 1 or 2.

7. a cross section of the bottom surface of the groove that is perpendicular to the front-rear direction has a shape that follows an upwardly convex arc, The radius of curvature of the arc increases toward the bow at least in the gradually increasing portion.

7. A watercraft according to claim 6.

8. a pair of the propellers arranged in the width direction of the hull, The hull has a pair of the grooves corresponding to the pair of propellers.

3. A vessel according to claim 1 or 2.

9. Each of the pair of shaft holes is located on the outer side in the width direction of the hull with respect to the center in the width direction of each of the pair of groove portions in a plan view.

9. The watercraft of claim 8.

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